Placoides are a type of ancient marine organism that belong to the group of placozoans. They are simple, flat, and multicellular creatures that typically have a disc-like shape. Placoides are known for their unique structure, which consists of a few layers of cells, allowing them to absorb nutrients directly from the surrounding water. These organisms are primarily found in shallow marine environments and play a role in the ecosystem by contributing to the breakdown of organic material. Their simple body plan and lifestyle make them an interesting subject for studying the evolution of multicellular life on Earth.